Probing a target, such as a printed circuit board (PCB), may be done in a number of different ways. One way to probe a PCB involves using a hand-forced connection (i.e., where a user manually presses a probe against the point or points to be probed). Another way to probe a PCB is via a solder-down connection. Sometimes, the probes themselves cannot make contact with a PCB due to mechanical interference (i.e. obstructions on the PCB, or close spacing of test points). In these situations, a smaller and more flexible probe may be able to make mechanical contact with the PCB, where a larger or rigid probe could not.
When a smaller more flexible probe is required, a common practice involves using two flexible wires to make contact with a PCB. Typically, one wire will be used for the signal path and one wire will be used for ground. However, using flexible wires to contact the PCB may result in a decrease in signal integrity as signal frequencies rise. For example, the loading on the target signal may become destructive, and the wire may distort the signal that a test instrument observes.